Dose Distribution in Pediatric CT Abdominal Examination: Phantom Study

Abstract

To keep radiation doses during computed tomography (CT) examinations as low as reasonably achievable, performing a detailed dose measurement is important. A flexible acrylic sheet roll CT dosimetry phantom (SRCT-P) with radiochromic film (RF) was developed to estimate in detail the dose distribution during pediatric CT examination. The SRCT-Ps were elliptically-shaped by rolling up flexible acrylic sheets (1.1 g/cm³). The dose distributions in the SRCT-P (body thickness and width: 6-8 cm [neonates], 10-12 cm [infants], and 14-16 cm [three-year-old children]) were evaluated. RFs were positioned from the center to the surface along the long- and short-axis directions in each SRCT-P. The scanning parameters of the single detector CT were 120 kV, 250 mA, 1.0 sec/rot, a slice thickness of 5 mm, and a 1.0 beam pitch. When the mean center dose at 10-12 cm on the SRCT-P was taken as 100%, the mean center doses at 6-8..or 14-16 cm were 145..or 43%, respectively, and the mean surface doses for 0, 90, and 180 degrees at 6-8, 10-12, and 14-16 cm of the SRCT-P were as follows: 158%, 159%, and 140%; 132%, 125%, and 116%; and 164%, 128%, and 131%, respectively. The center dose was increased with a decrease in the phantom size. The surface doses were decreased with decreasing phantom sizes of 14-16 to 10-12 cm; however, surface doses were increased with decreasing phantom sizes of 10-12 to 6-8 cm. The detail dose distribution of a CT examination can be measured separately by using a SRCT-P with a RF.